1. Field of Invention
The invention relates to a fan and a fan frame thereof, and in particular to a fan and a fan frame thereof having functions of airflow pressurizing and guiding.
2. Related Art
An electronic element, such as a CPU (Central Processing Unit), is usually disposed in a housing in order to protect the electronic element from being contaminated by the dust in the air. However, the operating electronic element generates heat, which has to be dissipated. If the heat is not dissipated appropriately, the stability and efficiency of the electronic element tend to deteriorate, or even the electronic element may burn out. Thus, a fan is usually used to keep the electronic element to work normally within an operational temperature range.
FIG. 1 is an exploded view showing a conventional fan, and FIG. 2 is a cross-sectional view showing the fan of FIG. 1. Referring to FIGS. 1 and 2, a conventional fan 1 includes a fan frame 10 and an impeller 20. The fan frame 10 has a housing 11, a base 12 and a plurality of ribs 13. The base 12 is disposed in the middle of the housing 11. The ribs 13 are disposed between the housing 11 and the base 12 for supporting the base 12. The impeller 20 is disposed in the housing 11 and located on the base 12. A motor 14 is also disposed on the base 12. When the fan 1 rotates, the motor 14 drives the impeller 20 to rotate for producing an airflow and enforcing the airflow to flow toward the electronic element (not shown) so as to dissipate the heat of the electronic element.
However, the operation voltage and the working frequency of the electronic element are increased with the increasing of the processing speed of the electronic element, and the temperature of the electronic element is also greatly increased. Thus, the air pressure and the air quantity of the fan 1 have to be increased for achieving the sufficient heat dissipating effect. The cross-sectional area of the flowing fluid is a main reason of determining the air quantity. However, the housing 11 of the conventional fan 1 has a uniform aperture. In other words, the cross-sectional area of an inlet 15 of the housing 11 is equal to the cross-sectional area of an outlet 16 of the housing 11. Thus, the air pressure and the air quantity of the fan 1 are restricted and cannot be effectively increased.
To solve this problem, the prior art usually increases the operational efficiency of the fan 1 or enlarges the impeller 20 so as to increase the air quantity of the fan 1. However, increasing the operational efficiency of the fan 1 has to pay for the extra power cost. Besides, the inner temperature of the fan 1 is inevitably increased, and the lifetime of the fan 1 is thus shortened. Furthermore, enlarging the impeller 20 has to satisfy the precondition of the enlarged housing 11 for accommodating the enlarged impeller 20. However, the size of the housing 11 is often restricted by the limited space in the casing of the electronic element and thus cannot be increased arbitrarily.
Thus, it is an important subject of the invention to provide a fan and a fan frame thereof capable of effectively increasing the air pressure and the air quantity of the fan without adding the extra power and enlarging the size of the fan.